Prior to last month's massive breach of federal employee records, the Office of Personnel Management's own inspector general repeatedly expressed concern over the agency's outdated security practices, according to a report.

According to "Handing Over the Keys to the Castle: OPM Demonstrated that Antiquated Security Practices Harm National Security," a report from the non-partisan think tank Institute for Critical Infrastructure Technology, the greatest failure behind the OPM breach was lack of a comprehensive governing policy for cybersecurity at the agency, which would have proactively controlled system access and mandated regular patches and upgrades. The breach reportedly impacted at least 22.5 million former, current and prospective U.S. employees.

"The single most significant recommendation that agencies like OPM could heed is to actually listen to the advice of the inspector general and do everything within their power to meet or exceed regulatory measures," the report stated.